By recycling and utilizing industrial furnace residual-heat, energy consumption can be saved, the production cost of the thermal product can be reduced, while the emission of the contaminant can be reduced. Industrial furnaces and kilns are large-sized high energy-consuming apparatuses with abundant residual-heat. With the rapid development of national economy, the industrial furnace has enormous utilizable potentiality. Iron and steel industry, carbide industry, alumina industry and refractory material industry are big energy consumers, and the rapid growth of the above industries drives the rapid development of industrial furnace. For thermal product, in the process of production, flue gas emission temperature is high, and is about 240 to 260° C. By effectively utilizing this part of the flue gas residual-heat, the energy waste can be reduced, and the economy and the environmental protection of the industrial furnace can be improved.
Since flue gas due to fuel combusting in a rotary kiln passes through calcinated material from a kiln chamber, harmful substances in the fuel are attached to the calcinated material, while dusts due to combusting fall on the material, thereby the quality of calcinated product is adversely affected. In addition, the flue gas after combusting and carbon dioxide due to limestone decomposing are mixed together, which is disadvantageous for recycling and utilization of carbon dioxide which is the calcinated by-product of limestone. The known rotary kiln can not be directly used for coking, coal gasification or semi-coke producing because calcination of processed material and combustion are performed in the same kiln chamber.